The present invention relates to a new and improved construction of an and apparatus for automatically compensating or evening the thickness or density fluctuations or variations at textile machines, such as cards, drawing frames and the like.
In the context of this disclosure the terms evening or compensating the "density" or "thickness" variations of the fiber or fibrous material, or equivalent expressions, are generally intended to mean essentially or substantially evening out or compensating such density or thickness variations or irregularities so that the fiber or fibrous material delivered by the textile machine possesses an essentially or substantially uniform weight per unit length or density.
Generally speaking, the apparatus for automatically compensating or evening thickness or density fluctuations in a fiber mass at textile machines, such as cards or carding machines, draw frames and the like, comprises means for deriving signals at the infeed or input side of the textile machine which are dependent upon the momentary density or thickness of the mass of fiber material, such as a batt or sliver, located in a fiber feed device and means for deriving signals at the output of the textile machine which are dependent upon the momentary thickness or density of the delivered mass of fiber material, such as a web or sliver at the output of the textile machine. These derived signals are processed in order to control the infeed speed of the mass of fiber material to the textile machine as a function of such derived signals.
In its broader aspects, the apparatus is manifested by the features that there is provided a fiber infeed means or device comprising at least one driven or driveable rotatable feed roll for feeding the fibrous material or fiber mass to the textile machine. A fiber feed element, typically but not exclusively a fiber feed plate, coacts with this driven rotatable feed roll and forms therebetween a nipping zone or region or gap for the fiber material. There is also provided a device or apparatus at the outlet or output side of the textile machine for determining the thickness or density of the delivered mass of fiber material, such as the delivered web or sliver. Such device may be of the type disclosed in the European Patent No. 78,393, published May 14, 1986 and the cognate U.S. Pat. No. 4,539,729, granted Sept. 10, 1985, the disclosure of which is incorporated herein by reference. Measuring or sensing means detect the fiber density or thickness variations prevailing in the nipping zone or region or gap--hereinafter usually simply referred to as the nipping zone or region--. Likewise, the measuring or sensing means detect the thickness or density of the delivered mass of fiber material. Each such measuring or sensing means deliver respective output signals in accordance with the detected or measured density or thickness of the corresponding mass of fiber material. To correct the variations in the fiber density or thickness infed into the textile machine the respective measuring or sensing means can deliver the detected or derived measuring signals to a control device or control for the evening or compensation of the density or thickness variations of the infed fiber material.
Evening or compensation of the density or thickness of fiber material at the input or input side of a textile machine, it being noted that in the case of a card such fiber material or mass is typically termed a fiber batt or lap, is an important prerequisite for the uniformity of the fiber product, again in the case of a card typically termed a web or sliver, delivered by the textile machine. This prerequisite or precondition assumes an even greater importance with increasing processing speeds of the textile machine because fewer machines are employed for the same quantity of fiber material, such as the batt or lap, which is to be processed, so that there is reduced the possibility of doubling throughout a larger number of machines.
Because of the importance of this problem there has evolved a considerable amount of patent documentation and literature proposing solutions attempting to fulfill such objectives. In the following description there will be enumerated, by way of example, a number of such patents.
For instance, in the U.S. Pat. No. 4,275,483, granted June 30, 1981, there is disclosed a fiber infeed means for a carding machine or card. The fiber infeed means comprises a stationarily arranged feed plate and a driven and movable feed roll arranged above the stationary feed plate. This driven and movable feed roll is pressed at both of its ends by means of springs against the fiber batt located between the driven and movable feed roll and the stationary feed plate.
The movements or displacements of the driven and movable feed roll, caused by the irregularities or unevenness in the fiber batt, are detected by displacement sensors or transducers provided at both ends of the driven and movable feed roll. These displacement sensors deliver signals representative of the irregularities in the fiber batt to a control device which computes therefrom the requisite change in the rotational speed of the driven and movable feed roll in order to compensate the unevenness or irregularity of the infed fiber batt as far as possible.
What is construed to be a notable shortcoming of this prior art system resides in the fact that the driven and movable feed roll, which infeeds the fiber material, is also used for sensing the unevenness of the fiber batt. This automatically leads to disturbances or deviations in the measuring signals, even then if measures are undertaken in the arrangement and construction of the drive system for the driven and movable feed roll in order to obtain directions of the drive forces at the driven and movable feed roll essentially perpendicular to the direction of movement of such driven and movable feed roll during the batt thickness sensing operation.
The aforementioned shortcoming or problem is considered to be eliminated by the apparatus disclosed in the French Patent No. 2,322,943, published Apr. 1, 1977, which proposes using a stationary but rotatable feed roll and sensing the unevenness or irregularities of the infed fiber material, namely the batt or lap delivered to the card, by means of a movable feed plate structure or unit which is preferably composed of a plurality of contiguous pedals or plates. The feed plate structure or unit, and specifically the pedals or plates thereof are mounted to be pivotable or swivelable, so that they can move towards and away from the stationary but rotational feed roll, to thereby sense unevenness or irregularities in the infed fiber material or batt.
A shortcoming which is thought to exist in this prior art system does not pertain so much to the actual measuring principle involved, but to the manner of transfer of the fibers to a subsequent licker-in cylinder or roll. Due to the aforementioned pivotability of the trough-like feed pedals or plates in relation to the stationary licker-in cylinder or roll the fiber transfer position or location at the feed plates or pedals, moves or shifts. Consequently, the position of the fiber transfer location of the fiber batt from the feed plates or pedals to the licker-in cylinder or roll likewise alternately moves in the direction of rotation of the licker-in cylinder or roll and in the opposite rotational sense or direction. This produces disturbances in the transfer of the fibers to the licker-in cylinder or roll.
A further state-of-the-art system which has been proposed, in order to eliminate or alleviate the initially explained drawbacks or shortcomings, has been described in the German Published Patent No. 2,912,576, published Oct. 31, 1979. In this prior art apparatus a sensor element which is provided near to or bordering the stationary trough-like feed plate detects the density of the fiber batt which is in contact with the trough-like feed plate and delivers an appropriate signal to a control device in order to regulate the rotational speed of the feed roll.
What is perceived to be a shortcoming in this prior art system resides in the fact that the measurement of the density of the fiber batt occurs prior to entry thereof between the trough-like feed plate and the feed roll. This too early or incipient fiber density sensing operation allows for variations in the density of the fiber batt to still occur up to the point of entry of the fiber batt between the trough-like feed plate and the feed roll. These fiber density variations then no longer coincide with or are no longer faithfully represented by the measured values.
By way of clarification, it is here mentioned that fundamentally a trough-like feed plate and a feed plate constitute comparable or the same type of elements and a feed cylinder and a feed roll likewise constitute comparable or the same type of elements. Therefore in the context of this disclosure this equatability, as stated above, should be kept in mind and is intended to be encompassed by the disclosure and teachings of the invention set forth herein.
The previously mentioned examples, as already discussed, relate to important but not however all of the preconditions or prerequisites for the uniformity or evenness of a mass of fiber material, such as a web or sliver, delivered by a textile machine.
A likewise essential precondition or prerequisite for the automatic compensation or evening of irregularities in a mass of fiber material, such as a fiber sliver, particularly in the case of a card or carding machine resides in the fact that the delivered mass of fiber material is controlled or checked in order to determine fiber loss between the point of infeed of the mass of fiber material, in the case of the card, the batt or lap, and the condensing of the fiber web at the outlet of the card.
The already heretofore mentioned German Patent No. 2,912.576, discloses and illustrates the combination of the already discussed compensation or evening of the infed fiber batt or lap, in conjunction with the control or checking of the fiber sliver at the outlet of the card or the drafting arrangement. However, this combination is likewise associated with the drawbacks heretofore considered in conjunction with such patent.